A head-up display apparatus has a combiner that is located in a vehicle, projects a display image to image a virtual image of a display image, and displays the image visible from a vehicle interior. For example, in a head-up display apparatus disclosed in patent literature 1, an upper end of the combiner is roughened by polishing or a rough mold inner surface. According to this configuration, an external light such as sunlight is diffused by the roughened upper end, and a reflection of the light in an observer's direction is prevented.
Generally, in the head-up display apparatus, an external light such as sunlight is input to the upper end of the combiner, and reflected from the upper end, and further reflected by a window shield, so that an occupant may visually recognize the virtual image of the upper. According to this difficulty, since the combiner upper end is viewed as a virtual image the display image displayed as the virtual image by the combiner, a forward visibility at the time of driving a vehicle may be deteriorated.
When the head-up display apparatus disclosed in patent literature 1 is studied, since an upper end of the combiner is roughened, the external light is diffused at random, and a part of the external light arrives at the window shield. As a result, the virtual image of the upper end can be viewed by the occupant.